[PATCH v2 0/8] MediaTek DisplayPort: support eDP and aux-bus

[PATCH v2 0/8] MediaTek DisplayPort: support eDP and aux-bus

[AngeloGioacchino Del Regno]

Changes in v2:
 - Sorry, the v1 send got broken as I forgot to remove old patches
   in my send folder.

This series adds "real" support for eDP in the mtk-dp DisplayPort driver.

Explaining the "real":
Before this change, the DisplayPort driver did support eDP to some
extent, but it was treating it entirely like a regular DP interface
which is partially fine, after all, embedded DisplayPort *is* actually
DisplayPort, but there might be some differences to account for... and
this is for both small performance improvements and, more importantly,
for correct functionality in some systems.

Functionality first:

One of the common differences found in various boards implementing eDP
and machines using an eDP panel is that many times the HPD line is not
connected. This *must* be accounted for: at startup, this specific IP
will raise a HPD interrupt (which should maybe be ignored... as it does
not appear to be a "real" event...) that will make the eDP panel to be
detected and to actually work but, after a suspend-resume cycle, there
will be no HPD interrupt (as there's no HPD line in my case!) producing
a functionality issue - specifically, the DP Link Training fails because
the panel doesn't get powered up, then it stays black and won't work
until rebooting the machine (or removing and reinserting the module I
think, but I haven't tried that).

Now for.. both:
eDP panels are *e*DP because they are *not* removable (in the sense that
you can't unplug the cable without disassembling the machine, in which
case, the machine shall be powered down..!): this (correct) assumption
makes us able to solve some issues and to also gain a little performance
during PM operations.

What was done here is:
 - Caching the EDID if the panel is eDP: we're always going to read the
   same data everytime, so we can just cache that (as it's small enough)
   shortening PM resume times for the eDP driver instance;
 - Always return connector_status_connected if it's eDP: non-removable
   means connector_status_disconnected can't happen during runtime...
   this also saves us some time and even power, as we won't have to
   perform yet another power cycle of the HW;
 - Added aux-bus support!
   This makes us able to rely on panel autodetection from the EDID,
   avoiding to add more and more panel timings to panel-edp and, even
   better, allowing to use one panel node in devicetrees for multiple
   variants of the same machine since, at that point, it's not important
   to "preventively know" what panel we have (eh, it's autodetected...!).

This was tested on a MT8195 Cherry Tomato Chromebook (panel-edp on aux-bus)


P.S.: For your own testing commodity, here's a reference devicetree:
&edp_tx {
	status = "okay";

	pinctrl-names = "default";
	pinctrl-0 = <&edptx_pins_default>;

	ports {
		#address-cells = <1>;
		#size-cells = <0>;

		port@0 {
			reg = <0>;
			edp_in: endpoint {
				remote-endpoint = <&dp_intf0_out>;
			};
		};

		port@1 {
			reg = <1>;
			edp_out: endpoint {
				data-lanes = <0 1 2 3>;
				remote-endpoint = <&panel_in>;
			};
		};
	};

	aux-bus {
		panel: panel {
			compatible = "edp-panel";
			power-supply = <&pp3300_disp_x>;
			backlight = <&backlight_lcd0>;
			port {
				panel_in: endpoint {
					remote-endpoint = <&edp_out>;
				};
			};
		};
	};
};

AngeloGioacchino Del Regno (8):
  drm/mediatek: dp: Cache EDID for eDP panel
  drm/mediatek: dp: Move AUX and panel poweron/off sequence to function
  drm/mediatek: dp: Always return connected status for eDP in .detect()
  drm/mediatek: dp: Always set cable_plugged_in at resume for eDP panel
  drm/mediatek: dp: Change logging to dev for mtk_dp_aux_transfer()
  drm/mediatek: dp: Enable event interrupt only when bridge attached
  drm/mediatek: dp: Use devm variant of drm_bridge_add()
  drm/mediatek: dp: Add support for embedded DisplayPort aux-bus

 drivers/gpu/drm/mediatek/mtk_dp.c | 172 ++++++++++++++++++------------
 1 file changed, 106 insertions(+), 66 deletions(-)

-- 
2.40.0

[PATCH v2 1/8] drm/mediatek: dp: Cache EDID for eDP panel

[AngeloGioacchino Del Regno]

Since eDP panels are not removable it is safe to cache the EDID:
this will avoid a relatively long read transaction at every PM
resume that is unnecessary only in the "special" case of eDP,
hence speeding it up a little, as from now on, as resume operation,
we will perform only link training.

Signed-off-by: AngeloGioacchino Del Regno <angelogioacchino.delregno@collabora.com>
---
 drivers/gpu/drm/mediatek/mtk_dp.c | 11 ++++++++++-
 1 file changed, 10 insertions(+), 1 deletion(-)

diff --git a/drivers/gpu/drm/mediatek/mtk_dp.c b/drivers/gpu/drm/mediatek/mtk_dp.c
index 1f94fcc144d3..84f82cc68672 100644
--- a/drivers/gpu/drm/mediatek/mtk_dp.c
+++ b/drivers/gpu/drm/mediatek/mtk_dp.c
@@ -118,6 +118,7 @@ struct mtk_dp {
 	const struct mtk_dp_data *data;
 	struct mtk_dp_info info;
 	struct mtk_dp_train_info train_info;
+	struct edid *edid;
 
 	struct platform_device *phy_dev;
 	struct phy *phy;
@@ -1993,7 +1994,11 @@ static struct edid *mtk_dp_get_edid(struct drm_bridge *bridge,
 		usleep_range(2000, 5000);
 	}
 
-	new_edid = drm_get_edid(connector, &mtk_dp->aux.ddc);
+	/* eDP panels aren't removable, so we can return a cached EDID. */
+	if (mtk_dp->edid && mtk_dp->bridge.type == DRM_MODE_CONNECTOR_eDP)
+		new_edid = drm_edid_duplicate(mtk_dp->edid);
+	else
+		new_edid = drm_get_edid(connector, &mtk_dp->aux.ddc);
 
 	/*
 	 * Parse capability here to let atomic_get_input_bus_fmts and
@@ -2022,6 +2027,10 @@ static struct edid *mtk_dp_get_edid(struct drm_bridge *bridge,
 		drm_atomic_bridge_chain_post_disable(bridge, connector->state->state);
 	}
 
+	/* If this is an eDP panel and the read EDID is good, cache it for later */
+	if (mtk_dp->bridge.type == DRM_MODE_CONNECTOR_eDP && !mtk_dp->edid && new_edid)
+		mtk_dp->edid = drm_edid_duplicate(new_edid);
+
 	return new_edid;
 }
 
-- 
2.40.0

[PATCH v2 2/8] drm/mediatek: dp: Move AUX and panel poweron/off sequence to function

[AngeloGioacchino Del Regno]

Everytime we run bridge detection and/or EDID read we run a poweron
and poweroff sequence for both the AUX and the panel; moreover, this
is also done when enabling the bridge in the .atomic_enable() callback.

Move this power on/off sequence to a new mtk_dp_aux_panel_poweron()
function as to commonize it.
Note that, before this commit, in mtk_dp_bridge_atomic_enable() only
the AUX was getting powered on but the panel was left powered off if
the DP cable wasn't plugged in while now we unconditionally send a D0
request and this is done for two reasons:
 - First, whether this request fails or not, it takes the same time
   and anyway the DP hardware won't produce any error (or, if it
   does, it's ignorable because it won't block further commands)
 - Second, training the link between a sleeping/standby/unpowered
   display makes little sense.

Signed-off-by: AngeloGioacchino Del Regno <angelogioacchino.delregno@collabora.com>
---
 drivers/gpu/drm/mediatek/mtk_dp.c | 76 ++++++++++++-------------------
 1 file changed, 30 insertions(+), 46 deletions(-)

diff --git a/drivers/gpu/drm/mediatek/mtk_dp.c b/drivers/gpu/drm/mediatek/mtk_dp.c
index 84f82cc68672..76ea94167531 100644
--- a/drivers/gpu/drm/mediatek/mtk_dp.c
+++ b/drivers/gpu/drm/mediatek/mtk_dp.c
@@ -1253,6 +1253,29 @@ static void mtk_dp_audio_mute(struct mtk_dp *mtk_dp, bool mute)
 			   val[2], AU_TS_CFG_DP_ENC0_P0_MASK);
 }
 
+static void mtk_dp_aux_panel_poweron(struct mtk_dp *mtk_dp, bool pwron)
+{
+	if (pwron) {
+		/* power on aux */
+		mtk_dp_update_bits(mtk_dp, MTK_DP_TOP_PWR_STATE,
+				   DP_PWR_STATE_BANDGAP_TPLL_LANE,
+				   DP_PWR_STATE_MASK);
+
+		/* power on panel */
+		drm_dp_dpcd_writeb(&mtk_dp->aux, DP_SET_POWER, DP_SET_POWER_D0);
+		usleep_range(2000, 5000);
+	} else {
+		/* power off panel */
+		drm_dp_dpcd_writeb(&mtk_dp->aux, DP_SET_POWER, DP_SET_POWER_D3);
+		usleep_range(2000, 3000);
+
+		/* power off aux */
+		mtk_dp_update_bits(mtk_dp, MTK_DP_TOP_PWR_STATE,
+				   DP_PWR_STATE_BANDGAP_TPLL,
+				   DP_PWR_STATE_MASK);
+	}
+}
+
 static void mtk_dp_power_enable(struct mtk_dp *mtk_dp)
 {
 	mtk_dp_update_bits(mtk_dp, MTK_DP_TOP_RESET_AND_PROBE,
@@ -1937,16 +1960,9 @@ static enum drm_connector_status mtk_dp_bdg_detect(struct drm_bridge *bridge)
 	if (!mtk_dp->train_info.cable_plugged_in)
 		return ret;
 
-	if (!enabled) {
-		/* power on aux */
-		mtk_dp_update_bits(mtk_dp, MTK_DP_TOP_PWR_STATE,
-				   DP_PWR_STATE_BANDGAP_TPLL_LANE,
-				   DP_PWR_STATE_MASK);
+	if (!enabled)
+		mtk_dp_aux_panel_poweron(mtk_dp, true);
 
-		/* power on panel */
-		drm_dp_dpcd_writeb(&mtk_dp->aux, DP_SET_POWER, DP_SET_POWER_D0);
-		usleep_range(2000, 5000);
-	}
 	/*
 	 * Some dongles still source HPD when they do not connect to any
 	 * sink device. To avoid this, we need to read the sink count
@@ -1958,16 +1974,8 @@ static enum drm_connector_status mtk_dp_bdg_detect(struct drm_bridge *bridge)
 	if (DP_GET_SINK_COUNT(sink_count))
 		ret = connector_status_connected;
 
-	if (!enabled) {
-		/* power off panel */
-		drm_dp_dpcd_writeb(&mtk_dp->aux, DP_SET_POWER, DP_SET_POWER_D3);
-		usleep_range(2000, 3000);
-
-		/* power off aux */
-		mtk_dp_update_bits(mtk_dp, MTK_DP_TOP_PWR_STATE,
-				   DP_PWR_STATE_BANDGAP_TPLL,
-				   DP_PWR_STATE_MASK);
-	}
+	if (!enabled)
+		mtk_dp_aux_panel_poweron(mtk_dp, false);
 
 	return ret;
 }
@@ -1983,15 +1991,7 @@ static struct edid *mtk_dp_get_edid(struct drm_bridge *bridge,
 
 	if (!enabled) {
 		drm_atomic_bridge_chain_pre_enable(bridge, connector->state->state);
-
-		/* power on aux */
-		mtk_dp_update_bits(mtk_dp, MTK_DP_TOP_PWR_STATE,
-				   DP_PWR_STATE_BANDGAP_TPLL_LANE,
-				   DP_PWR_STATE_MASK);
-
-		/* power on panel */
-		drm_dp_dpcd_writeb(&mtk_dp->aux, DP_SET_POWER, DP_SET_POWER_D0);
-		usleep_range(2000, 5000);
+		mtk_dp_aux_panel_poweron(mtk_dp, true);
 	}
 
 	/* eDP panels aren't removable, so we can return a cached EDID. */
@@ -2015,15 +2015,7 @@ static struct edid *mtk_dp_get_edid(struct drm_bridge *bridge,
 	}
 
 	if (!enabled) {
-		/* power off panel */
-		drm_dp_dpcd_writeb(&mtk_dp->aux, DP_SET_POWER, DP_SET_POWER_D3);
-		usleep_range(2000, 3000);
-
-		/* power off aux */
-		mtk_dp_update_bits(mtk_dp, MTK_DP_TOP_PWR_STATE,
-				   DP_PWR_STATE_BANDGAP_TPLL,
-				   DP_PWR_STATE_MASK);
-
+		mtk_dp_aux_panel_poweron(mtk_dp, false);
 		drm_atomic_bridge_chain_post_disable(bridge, connector->state->state);
 	}
 
@@ -2188,15 +2180,7 @@ static void mtk_dp_bridge_atomic_enable(struct drm_bridge *bridge,
 		return;
 	}
 
-	/* power on aux */
-	mtk_dp_update_bits(mtk_dp, MTK_DP_TOP_PWR_STATE,
-			   DP_PWR_STATE_BANDGAP_TPLL_LANE,
-			   DP_PWR_STATE_MASK);
-
-	if (mtk_dp->train_info.cable_plugged_in) {
-		drm_dp_dpcd_writeb(&mtk_dp->aux, DP_SET_POWER, DP_SET_POWER_D0);
-		usleep_range(2000, 5000);
-	}
+	mtk_dp_aux_panel_poweron(mtk_dp, true);
 
 	/* Training */
 	ret = mtk_dp_training(mtk_dp);
-- 
2.40.0

[PATCH v2 3/8] drm/mediatek: dp: Always return connected status for eDP in .detect()

[AngeloGioacchino Del Regno]

If this is an eDP panel it's not removable, hence it's always connected:
as a shortcut, always return connector_status_connected in the .detect()
callback for eDP connector, avoiding a poweron, a check for sink count
and a poweroff.

Signed-off-by: AngeloGioacchino Del Regno <angelogioacchino.delregno@collabora.com>
---
 drivers/gpu/drm/mediatek/mtk_dp.c | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/drivers/gpu/drm/mediatek/mtk_dp.c b/drivers/gpu/drm/mediatek/mtk_dp.c
index 76ea94167531..c82dd1f0675d 100644
--- a/drivers/gpu/drm/mediatek/mtk_dp.c
+++ b/drivers/gpu/drm/mediatek/mtk_dp.c
@@ -1957,6 +1957,9 @@ static enum drm_connector_status mtk_dp_bdg_detect(struct drm_bridge *bridge)
 	bool enabled = mtk_dp->enabled;
 	u8 sink_count = 0;
 
+	if (mtk_dp->bridge.type == DRM_MODE_CONNECTOR_eDP)
+		return connector_status_connected;
+
 	if (!mtk_dp->train_info.cable_plugged_in)
 		return ret;
 
-- 
2.40.0

[PATCH v2 4/8] drm/mediatek: dp: Always set cable_plugged_in at resume for eDP panel

[AngeloGioacchino Del Regno]

eDP panels are not removable: at PM resume, the cable will obviously
still be plugged in.

Signed-off-by: AngeloGioacchino Del Regno <angelogioacchino.delregno@collabora.com>
---
 drivers/gpu/drm/mediatek/mtk_dp.c | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/drivers/gpu/drm/mediatek/mtk_dp.c b/drivers/gpu/drm/mediatek/mtk_dp.c
index c82dd1f0675d..ac21eca0e20e 100644
--- a/drivers/gpu/drm/mediatek/mtk_dp.c
+++ b/drivers/gpu/drm/mediatek/mtk_dp.c
@@ -2607,6 +2607,9 @@ static int mtk_dp_resume(struct device *dev)
 	mtk_dp_hwirq_enable(mtk_dp, true);
 	mtk_dp_power_enable(mtk_dp);
 
+	if (mtk_dp->bridge.type == DRM_MODE_CONNECTOR_eDP)
+		mtk_dp->train_info.cable_plugged_in = true;
+
 	return 0;
 }
 #endif
-- 
2.40.0

[PATCH v2 5/8] drm/mediatek: dp: Change logging to dev for mtk_dp_aux_transfer()

[AngeloGioacchino Del Regno]

Change logging from drm_{err,info}() to dev_{err,info}() in functions
mtk_dp_aux_transfer() and mtk_dp_aux_do_transfer(): this will be
essential to avoid getting NULL pointer kernel panics if any kind
of error happens during AUX transfers happening before the bridge
is attached.

This may potentially start happening in a later commit implementing
aux-bus support, as AUX transfers will be triggered from the panel
driver (for EDID) before the mtk-dp bridge gets attached, and it's
done in preparation for the same.

Signed-off-by: AngeloGioacchino Del Regno <angelogioacchino.delregno@collabora.com>
---
 drivers/gpu/drm/mediatek/mtk_dp.c | 6 +++---
 1 file changed, 3 insertions(+), 3 deletions(-)

diff --git a/drivers/gpu/drm/mediatek/mtk_dp.c b/drivers/gpu/drm/mediatek/mtk_dp.c
index ac21eca0e20e..19b145cf2e05 100644
--- a/drivers/gpu/drm/mediatek/mtk_dp.c
+++ b/drivers/gpu/drm/mediatek/mtk_dp.c
@@ -849,7 +849,7 @@ static int mtk_dp_aux_do_transfer(struct mtk_dp *mtk_dp, bool is_read, u8 cmd,
 		u32 phy_status = mtk_dp_read(mtk_dp, MTK_DP_AUX_P0_3628) &
 				 AUX_RX_PHY_STATE_AUX_TX_P0_MASK;
 		if (phy_status != AUX_RX_PHY_STATE_AUX_TX_P0_RX_IDLE) {
-			drm_err(mtk_dp->drm_dev,
+			dev_err(mtk_dp->dev,
 				"AUX Rx Aux hang, need SW reset\n");
 			return -EIO;
 		}
@@ -2061,7 +2061,7 @@ static ssize_t mtk_dp_aux_transfer(struct drm_dp_aux *mtk_aux,
 		is_read = true;
 		break;
 	default:
-		drm_err(mtk_aux->drm_dev, "invalid aux cmd = %d\n",
+		dev_err(mtk_dp->dev, "invalid aux cmd = %d\n",
 			msg->request);
 		ret = -EINVAL;
 		goto err;
@@ -2077,7 +2077,7 @@ static ssize_t mtk_dp_aux_transfer(struct drm_dp_aux *mtk_aux,
 					     to_access);
 
 		if (ret) {
-			drm_info(mtk_dp->drm_dev,
+			dev_info(mtk_dp->dev,
 				 "Failed to do AUX transfer: %d\n", ret);
 			goto err;
 		}
-- 
2.40.0

[PATCH v2 6/8] drm/mediatek: dp: Enable event interrupt only when bridge attached

[AngeloGioacchino Del Regno]

In preparation for implementing support for aux-bus in this driver,
add a IRQ_NOAUTOEN flag to the event interrupt that we request at
probe time and manage the enablement of the ISR at bridge_attach
and detach time.

When aux-bus will be implemented, enabling the interrupt before
attaching the bridge will create an event storm and hang the kernel
during boot.
In any case, the interrupt handler anyway requires resources that
are initialized by mtk_dp_bridge_attach(), so it cannot do anything
meaningful without... and even crash, but that's not happening in
the current code because the HW remains unpowered until resources
are made available.

Signed-off-by: AngeloGioacchino Del Regno <angelogioacchino.delregno@collabora.com>
---
 drivers/gpu/drm/mediatek/mtk_dp.c | 15 ++++++++++-----
 1 file changed, 10 insertions(+), 5 deletions(-)

diff --git a/drivers/gpu/drm/mediatek/mtk_dp.c b/drivers/gpu/drm/mediatek/mtk_dp.c
index 19b145cf2e05..6aaf162a6bfe 100644
--- a/drivers/gpu/drm/mediatek/mtk_dp.c
+++ b/drivers/gpu/drm/mediatek/mtk_dp.c
@@ -100,6 +100,7 @@ struct mtk_dp_efuse_fmt {
 struct mtk_dp {
 	bool enabled;
 	bool need_debounce;
+	int irq;
 	u8 max_lanes;
 	u8 max_linkrate;
 	u8 rx_cap[DP_RECEIVER_CAP_SIZE];
@@ -2148,6 +2149,8 @@ static int mtk_dp_bridge_attach(struct drm_bridge *bridge,
 
 	mtk_dp->drm_dev = bridge->dev;
 
+	irq_clear_status_flags(mtk_dp->irq, IRQ_NOAUTOEN);
+	enable_irq(mtk_dp->irq);
 	mtk_dp_hwirq_enable(mtk_dp, true);
 
 	return 0;
@@ -2164,6 +2167,7 @@ static void mtk_dp_bridge_detach(struct drm_bridge *bridge)
 	struct mtk_dp *mtk_dp = mtk_dp_from_bridge(bridge);
 
 	mtk_dp_hwirq_enable(mtk_dp, false);
+	disable_irq(mtk_dp->irq);
 	mtk_dp->drm_dev = NULL;
 	mtk_dp_poweroff(mtk_dp);
 	drm_dp_aux_unregister(&mtk_dp->aux);
@@ -2482,7 +2486,7 @@ static int mtk_dp_probe(struct platform_device *pdev)
 {
 	struct mtk_dp *mtk_dp;
 	struct device *dev = &pdev->dev;
-	int ret, irq_num;
+	int ret;
 
 	mtk_dp = devm_kzalloc(dev, sizeof(*mtk_dp), GFP_KERNEL);
 	if (!mtk_dp)
@@ -2491,9 +2495,9 @@ static int mtk_dp_probe(struct platform_device *pdev)
 	mtk_dp->dev = dev;
 	mtk_dp->data = (struct mtk_dp_data *)of_device_get_match_data(dev);
 
-	irq_num = platform_get_irq(pdev, 0);
-	if (irq_num < 0)
-		return dev_err_probe(dev, irq_num,
+	mtk_dp->irq = platform_get_irq(pdev, 0);
+	if (mtk_dp->irq < 0)
+		return dev_err_probe(dev, mtk_dp->irq,
 				     "failed to request dp irq resource\n");
 
 	mtk_dp->next_bridge = devm_drm_of_get_bridge(dev, dev->of_node, 1, 0);
@@ -2514,7 +2518,8 @@ static int mtk_dp_probe(struct platform_device *pdev)
 
 	spin_lock_init(&mtk_dp->irq_thread_lock);
 
-	ret = devm_request_threaded_irq(dev, irq_num, mtk_dp_hpd_event,
+	irq_set_status_flags(mtk_dp->irq, IRQ_NOAUTOEN);
+	ret = devm_request_threaded_irq(dev, mtk_dp->irq, mtk_dp_hpd_event,
 					mtk_dp_hpd_event_thread,
 					IRQ_TYPE_LEVEL_HIGH, dev_name(dev),
 					mtk_dp);
-- 
2.40.0

[PATCH v2 7/8] drm/mediatek: dp: Use devm variant of drm_bridge_add()

[AngeloGioacchino Del Regno]

In preparation for adding support for aux-bus, which will add a code
path that may fail after the drm_bridge_add() call, change that to
devm_drm_bridge_add() to simplify failure paths later.

Signed-off-by: AngeloGioacchino Del Regno <angelogioacchino.delregno@collabora.com>
---
 drivers/gpu/drm/mediatek/mtk_dp.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/gpu/drm/mediatek/mtk_dp.c b/drivers/gpu/drm/mediatek/mtk_dp.c
index 6aaf162a6bfe..62d53c4b3feb 100644
--- a/drivers/gpu/drm/mediatek/mtk_dp.c
+++ b/drivers/gpu/drm/mediatek/mtk_dp.c
@@ -2565,7 +2565,7 @@ static int mtk_dp_probe(struct platform_device *pdev)
 		DRM_BRIDGE_OP_DETECT | DRM_BRIDGE_OP_EDID | DRM_BRIDGE_OP_HPD;
 	mtk_dp->bridge.type = mtk_dp->data->bridge_type;
 
-	drm_bridge_add(&mtk_dp->bridge);
+	devm_drm_bridge_add(dev, &mtk_dp->bridge);
 
 	mtk_dp->need_debounce = true;
 	timer_setup(&mtk_dp->debounce_timer, mtk_dp_debounce_timer, 0);
-- 
2.40.0

[PATCH v2 8/8] drm/mediatek: dp: Add support for embedded DisplayPort aux-bus

[AngeloGioacchino Del Regno]

For the eDP case we can support using aux-bus on MediaTek DP: this
gives us the possibility to declare our panel as generic "panel-edp"
which will automatically configure the timings and available modes
via the EDID that we read from it.

To do this, move the panel parsing at the end of the probe function
so that the hardware is initialized beforehand and also power it on
as, when we populate the aux-bus, the panel driver will trigger an
EDID read as panel detection.

**** CUT ****
Also, since the DP IP will always trigger a HPD interrupt at this
stage, it was necessary to add a new `bridge_attached` member to
the mtk_dp structure to make sure that `drm_helper_hpd_irq_event()`
will not be called before the bridge gets actually attached, or
otherwise we will get a NULL pointer KP due to mtk_dp->bridge.dev
being uninitialized.
**** CUT ****

Last but not least, since now the AUX transfers can happen in the
separated aux-bus, it was necessary to add an exclusion for the
cable_plugged_in check in `mtk_dp_aux_transfer()` and the easiest
way to do this is to simply ignore checking that when the bridge
type is eDP.

Signed-off-by: AngeloGioacchino Del Regno <angelogioacchino.delregno@collabora.com>
---
 drivers/gpu/drm/mediatek/mtk_dp.c | 56 +++++++++++++++++++++++++------
 1 file changed, 46 insertions(+), 10 deletions(-)

diff --git a/drivers/gpu/drm/mediatek/mtk_dp.c b/drivers/gpu/drm/mediatek/mtk_dp.c
index 62d53c4b3feb..f62ef24db67d 100644
--- a/drivers/gpu/drm/mediatek/mtk_dp.c
+++ b/drivers/gpu/drm/mediatek/mtk_dp.c
@@ -4,6 +4,7 @@
  * Copyright (c) 2022 BayLibre
  */
 
+#include <drm/display/drm_dp_aux_bus.h>
 #include <drm/display/drm_dp.h>
 #include <drm/display/drm_dp_helper.h>
 #include <drm/drm_atomic_helper.h>
@@ -2041,7 +2042,8 @@ static ssize_t mtk_dp_aux_transfer(struct drm_dp_aux *mtk_aux,
 
 	mtk_dp = container_of(mtk_aux, struct mtk_dp, aux);
 
-	if (!mtk_dp->train_info.cable_plugged_in) {
+	if (mtk_dp->bridge.type != DRM_MODE_CONNECTOR_eDP &&
+	    !mtk_dp->train_info.cable_plugged_in) {
 		ret = -EAGAIN;
 		goto err;
 	}
@@ -2153,6 +2155,11 @@ static int mtk_dp_bridge_attach(struct drm_bridge *bridge,
 	enable_irq(mtk_dp->irq);
 	mtk_dp_hwirq_enable(mtk_dp, true);
 
+	if (mtk_dp->bridge.type == DRM_MODE_CONNECTOR_eDP /* && panel_on_aux_bus() */) {
+		mtk_dp->train_info.cable_plugged_in = true;
+		drm_helper_hpd_irq_event(mtk_dp->drm_dev);
+	}
+
 	return 0;
 
 err_bridge_attach:
@@ -2482,6 +2489,20 @@ static int mtk_dp_register_audio_driver(struct device *dev)
 	return PTR_ERR_OR_ZERO(mtk_dp->audio_pdev);
 }
 
+static int mtk_dp_edp_link_panel(struct drm_dp_aux *mtk_aux)
+{
+	struct mtk_dp *mtk_dp = container_of(mtk_aux, struct mtk_dp, aux);
+	struct device *dev = mtk_aux->dev;
+	struct drm_bridge *panel_aux_bridge;
+
+	panel_aux_bridge = devm_drm_of_get_bridge(dev, dev->of_node, 1, 0);
+	if (IS_ERR(panel_aux_bridge))
+		return PTR_ERR(panel_aux_bridge);
+
+	mtk_dp->next_bridge = panel_aux_bridge;
+	return 0;
+}
+
 static int mtk_dp_probe(struct platform_device *pdev)
 {
 	struct mtk_dp *mtk_dp;
@@ -2500,21 +2521,14 @@ static int mtk_dp_probe(struct platform_device *pdev)
 		return dev_err_probe(dev, mtk_dp->irq,
 				     "failed to request dp irq resource\n");
 
-	mtk_dp->next_bridge = devm_drm_of_get_bridge(dev, dev->of_node, 1, 0);
-	if (IS_ERR(mtk_dp->next_bridge) &&
-	    PTR_ERR(mtk_dp->next_bridge) == -ENODEV)
-		mtk_dp->next_bridge = NULL;
-	else if (IS_ERR(mtk_dp->next_bridge))
-		return dev_err_probe(dev, PTR_ERR(mtk_dp->next_bridge),
-				     "Failed to get bridge\n");
-
 	ret = mtk_dp_dt_parse(mtk_dp, pdev);
 	if (ret)
 		return dev_err_probe(dev, ret, "Failed to parse dt\n");
 
-	drm_dp_aux_init(&mtk_dp->aux);
 	mtk_dp->aux.name = "aux_mtk_dp";
+	mtk_dp->aux.dev = dev;
 	mtk_dp->aux.transfer = mtk_dp_aux_transfer;
+	drm_dp_aux_init(&mtk_dp->aux);
 
 	spin_lock_init(&mtk_dp->irq_thread_lock);
 
@@ -2570,6 +2584,28 @@ static int mtk_dp_probe(struct platform_device *pdev)
 	mtk_dp->need_debounce = true;
 	timer_setup(&mtk_dp->debounce_timer, mtk_dp_debounce_timer, 0);
 
+	if (mtk_dp->bridge.type == DRM_MODE_CONNECTOR_eDP) {
+		/* Need to power on HW because aux-bus will read EDID */
+		mtk_dp_aux_panel_poweron(mtk_dp, true);
+
+		ret = devm_of_dp_aux_populate_bus(&mtk_dp->aux, NULL);
+
+		/* Power off AUX and panel now as detection is done. */
+		mtk_dp_aux_panel_poweron(mtk_dp, false);
+
+		/* We ignore -ENODEV error, as the panel may not be on aux-bus */
+		if (ret && ret != -ENODEV)
+			return ret;
+
+		/*
+		 * Here we don't ignore any error, as if there's no panel to
+		 * link, eDP is not configured correctly and will be unusable.
+		 */
+		ret = mtk_dp_edp_link_panel(&mtk_dp->aux);
+		if (ret)
+			return ret;
+	}
+
 	pm_runtime_enable(dev);
 	pm_runtime_get_sync(dev);
 
-- 
2.40.0